Cellulose fibers currently available in the market do not exhibit all desired properties for use in certain applications. For example, in the manufacture of automotive oil and air filters, it is desirable that the fibers exhibit reduced WRV and produce structures (e.g., filters) with high permeability and bulk with adequate sheet strength. However, one commercially available fiber produces structures with high permeability and bulk but does not have adequate sheet strength. Another commercially available fiber produces structures with higher permeability and bulk, but is brittle and loses permeability under conventional refining conditions. Another commercially available fiber produces structures with high permeability and bulk, but has an undesirably high WRV. Thus, there is a need in the art for improved cellulose fibers having reduced WRV that can produce structures with high permeability and bulk.
Attempts have been made to improve conventional manufacturing processes to obtain cellulose fibers of desired properties. For example, Shaw et al. describe in U.S. Pat. No. 3,819,470 that swellability, which is a result of water absorption, can be reduced by treating fibers with a substantive polymeric compound and fluff-drying. Adjusting parameters for improving quality of cellulose fibers are described in U.S. Pat. No: 3,756,913 to Wodka; U.S. Pat. No: 4,361,463 to Lindberg et al.; U.S. Pat. No: 4,853,086 to Graef; U.S. Pat. No: 2,926,116 to Keim et al.; and U.S. Pat. Nos: 5,200,036 and 5,015,245 to Noda. All patents (and references therein) cited herein are incorporated by reference. However, cellulose fibers that exhibit the desired properties as described herein have not been previously reported.